Multi-objective hierarchical optimisation design and experimental verification of an alterable-magnetic-circuit variable-flux memory machine

Rare-earth permanent magnet synchronous machines face challenges in manipulating their magnetic fields, which hinders the ability to extend the operation speed range. Moreover, this inflexibility leads to reduced efficiency in high-speed scenarios when the machine is under flux-weakening control and increases the risk of the magnets becoming demagnetised. The authors propose an alterable-magnetic-circuit variable-flux memory machine (AMC-VFMM) and a multi-objective hierarchical optimisation method is conducted to optimise the machine. Firstly, the topology and alterable-magnetic-circuit principle of the proposed AMC-VFMM are introduced. Then, optimisation objectives including torque production capability, flux regulation capability, and resisting unintentional demagnetisation capability are defined, and the hierarchical optimisation approach is established by stratifying the optimisation objectives and variables through the sensitivity analysis. Finite element analysis indicates that electromagnetic performances of the optimised design scheme are significantly enhanced. The bench test of the prototype demonstrates the superiority of the proposed AMC-VFMM and validates the effectiveness of the optimisation design method.